Causes, Effects and Precautions Against Earthquake

Created by: Group# 26Muhammad Saqalin, Mohib Abbas, Shahrukh Khan, and Inam

Ullah.

The University of Lahore, Islamabad Campus

What is Earthquake?

An earthquake is a sudden movement of earth's crust which lasts for a very short time.

It originates naturally at or below the surface of the earth.

Earthquake occurs all time, all over the earth. There are about 800 of them everyday but we often hear about the earthquake in news only once. This is because the vast majority of these quakes are very week.

Major earthquakes are very much less

frequent but are most destructive. It usually do not occur alone; when one such earthquake happens, there is usually another one at a nearby location.

An earthquake also has foreshocks. These

are smaller earthquakes that happen in the same place before the larger earthquake follows.

Effects of an Earthquake:

1. Earthquake causes damage to the building, bridges, dams…

2. Earthquake in many cases can cause great loss of life.

3. Earthquake can also cause floods and landslides. Landslides, triggered by earthquake, often cause more destruction than the earthquake themselves.

4. If the earthquake happens to be beneath the ocean floor, they can lead to a tsunami.

Causes of Earthquake:

Perhaps the earth is made up of three layers. At its heart is a core of iron, consisting of a solid sphere surrounded by a layer of hot, molten iron. Around the core is a mantle of soft, paste like rocks. And over the mantle rests the hard layer of rocks we call the crust. This crust is not a uniform, faultless shell. It is more like a jigsaw of blocks that fit together. The huge blocks that make up the crust are called tectonic plates.

The heat inside the earth sets up a current in the mantle, keeping it in constant motion. This makes the plates of the crust move continually. The movement sometimes causes the edges of the plates to grind against each other with a lot of force.

They may then get deformed, displaced, crushed or fractured. They may also slide under each other or move apart. Such changes in the plates send a set up vibrations through the crust, causing what we call an earthquake.

Other causes:

Earthquakes can occur due to reasons other than plate movements. Volcanic activity can cause earthquakes, as can human activities like nuclear explosions carried out underground. The collapse of mines has also been known to cause minor earthquakes.

Dams: The build-up of pressure due to the storage of a

large amount of water in the reservoirs behind large dams is considered to be a potential cause of earthquakes.

Tsunamis:Tsunami is a Japanese word meaning ‘harbour wave’. Earthquakes below the sea can cause tsunamis. The waves are usually not very high in the deep sea, where they originate. But when they reach the coast, they rise high like massive walls of water.They sweep over the land, submerging everything in sight within a very short time. And when they recede, they take with them everything that they have touched.

Weak points:

Over millions of years, the movements of the tectonic plates have created mountains and valleys on the surface of the earth. They have also created certain weak points, called faults, in the crust. Most faults occur along the boundaries of the tectonic plates and these are the zones where earthquakes occur.

Earthquake activity in Pakistan is mainly concentrated in the north and western sections of the country, along the boundary of the Indian plate and the Iranian and Afghan micro-plates. 

Faults (Pakistan):

• The Chaman Fault runs along Pakistan’s western frontier with Afghanistan from Kalat, in the northern Makran range, past Quetta and then on to Kabul, Afghanistan.

• A fault also runs along the Makran coast and is believed to be of the same nature as the West Coast fault along the coast of Maharashtra, India.

Earthquakes in Pakistan:

• The earthquake that struck Azad Kashmir, Islamabad, and Khyber Pakhtunkhwa in 2005 occurred in a place (Muzaffarabad). It registered a moment magnitude of 7.6 and had a maximum intensity. More than 80,000 people died in the earthquake.

• The 2013 Baluchistan earthquakes took place in late September in southwestern Pakistan. The mainshock had a moment magnitude of 7.7 and had a maximum intensity (Very Strong). At least 825 people were killed and hundreds more were injured.

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Casualties in Pak-istan

Measuring an Earthquake:

Earthquakes usually start at a depth of less than 100 km below the ground. The point of origin, called the seismic focus, is located  with the help of seismographs. (an instrument that measures and records details of earthquakes, such as force and duration).

Vibrations spread out from the Focus, like ripples in a pool of water. The location on the surface of the earth directly above the focus is called the epicenter. It normally bears the brunt(shocks) of the destructive power of these vibrations. That is to say, this is where the maximum damage normally occurs.

The extent of the damage depends on the strength of the vibrations or the energy associated with them. It also depends on the density of population (how many people live in an area) and the way buildings are constructed. The nature of the soil is another factor which determines the extent of damage. If the soil is loose and damp, the damage is greater than if it is hard and firm. This is why the severity of an earthquake is measured in two ways—in terms of its magnitude and in terms of its intensity.

Richter scale:

The magnitude of an earthquake depends on the energy of the vibrations. It is measured by seismographs on a scale called the Richter scale. Ranging from 1 to 10, for indicating the intensity of an earthquake.

Mercalli intensity scale:

The Mercalli intensity scale is a Seismic Scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake.

Protection against earthquake:

• All the building in seismic zones need be designed so that they can withstand major tremors(shakes). It is advisable to make the structure simple so that it is 'Quake Safe'.

• Since some building may catch fire, it is necessary that all the building have their fire fighting equipment in order.

• Safer places indoors, as well as outdoors, must be clearly identified.

• An emergency communication plan should be made available.

. Disaster management supplies (like flashlights, first aid box etc.) should be available on hand.

Safety Precautions during Earthquake:

For a person present inside of a building:

1. Take shelter under a table and stay there till the shaking stops.

2. Stay away from tall and heavy objects that may fall on you.

3. Do not get up, if you are in bed. Protect your head with pillows. 

4. Stay indoor until shaking stops and it is safe to move outside. Most of injuries occur when people, inside the building, attempts to move to a different location within the building or try to leave it.

For a person caught outside in the open:

1. Find a clear spot, away from buildings, trees, bridges and overhead power lines. Drop to the ground.

2. Do not come out, if in a moving vehicle. Drive slowly to a clear spot and stay inside. Come out only when the tremors stop.

Safety Precautions After the Earthquake:

1. Stay calm for a while. Expect after shocks. These shocks can cause additional damage.

2. Beware of possible tsunami, if you live in coastal area.

3. Carefully inspect utilities/supplies.

4. Use telephones only in emergency.

5. Stay away from damaged areas.

6. Help the injured ones.

THE ENDTHANKS